Portable wireless machine

ABSTRACT

An upper case ( 1 ) is connected to a lower case ( 2 ) in a hinge portion ( 3 ) so as to freely rotate. A plate shaped conductor ( 4 ) and a plate shaped conductor ( 5 ) are disposed along the surface of the case in the upper case ( 1 ). A ground plate ( 6 ) is formed in a ground pattern of a circuit board disposed in the lower case ( 2 ). The plate shaped conductor ( 4 ) and the plate shaped conductor ( 5 ) are selected by a high frequency switch ( 14 ) and connected to one end of a feeding portion ( 15 ). The other end of the feeding portion ( 15 ) is connected to the ground plate ( 6 ) to form a dipole antenna.

TECHNICAL FIELD

The present invention relates to a portable radio device such as aportable telephone, and more particularly to a portable radio devicehaving a collapsible casing.

BACKGROUND ART

A portable radio device with a collapsible structure ordinarily has amechanism including an upper casing and a lower casing connected by ahinge so as to be freely open and close. Thus, the portable radio devicecan take an opening state and a closing state. The portable radio devicehas two advantages of a high visibility and an easy portability that aviewable display screen can be enlarged under a state that the device isopened and used (namely, an opening state) and the device can be madecompact under a state that the device is closed and used (a closingstate) from the viewpoint of such structural characteristics.

As an antenna of a foldable portable telephone, a protrusion typeantenna disposed in a casing is disclosed in JP-A-2001-45123.

For such a protrusion type antenna, a helical antenna or an extensiblemono-pole antenna is ordinarily employed. Since the antenna portionprotrudes from the casing, an antenna gain can be raised while a handholds the portable telephone.

However, since the antenna portion is protruded, when the portabletelephone is taken out from a pocket or the like, the antenna may besometimes caught by a part of the pocket so that the portable telephoneis hardly taken out.

As compared therewith, as an antenna contained in the casing of thefoldable portable telephone, a strip line antenna is disclosed inJP-A-10-308618. Further, in JP-A-2001-284934, a hinge portion containedantenna is disclosed. Further, in JP-A-2001-156898, an antenna containedin an upper casing is disclosed.

Still further, as a flip type antenna contained in the casing of theportable telephone, a coil type antenna is described in JP-A-9-64778 anda micro-strip line antenna is described in JP-A-10-190330.

Further, JP-A-10-84406 discloses a plurality of element containedantenna in which a dipole antenna as a radiation element contained in anupper casing is combined with a non-feeding element contained in a lowercasing.

Since the above-described antenna contained in the casing has no partprotruding from the casing, the antenna is not caught by a part of thepocket or the like. However, since the direction of a main polarizedwave emitted from the antenna is limited to a specific direction, adifference is undesirably generated in the antenna gain between a casethat the portable telephone is held by a left hand during speaking (aleft hand speaking state) and a case that the portable telephone is heldby a right hand (a right hand speaking state).

Further, in the hinge portion contained antenna, under a state in whichthe portable telephone is allowed to come near to the ear and the mouthto speak (refer this state as to a speaking state, hereinafter), whenthe hinge portion is held by a hand, the antenna gain may be sometimesundesirably deteriorated, because the antenna portion is covered withthe hand.

Further, in the flip part contained antenna, while the flip part isclosed, a portable telephone main body is allowed to come near to theantenna portion so that the antenna gain may be possibly deteriorated.

Still further, in the plurality of element contained antenna, while theupper and lower casings are opened to speak, when a part near theradiation element is covered with a hand, the antenna gain may beundesirably deteriorated.

It is an object of the present invention to provide a portable radiodevice having an antenna with a high performance under various usingstates.

DISCLOSURE OF THE INVENTION

A portable radio device according to the present invention comprises: afirst casing; a second casing; a connection portion connecting the firstcasing to the second casing so as to freely rotate; a first antennaelement provided in the first casing; a conductor element provided inthe second casing to form a dipole antenna together with the firstantenna element; and a feeding portion having one end electricallyconnected to the first antenna element and the other end electricallyconnected to the conductor element.

According to this structure, the antenna elements respectivelyaccommodated in the first and second casings integrally operate as thedipole antenna. Thus, under a using state in which the portable radiodevice is held by a hand, a high antenna gain can be operationallyobtained.

Further, in the portable radio device according to the presentinvention, a plurality of first antenna elements are provided in thefirst casing and a switching portion is further provided for switchingthe plurality of first antenna elements to connect them to the feedingportion.

According to this structure, a directional diversity effect can beobtained. Under a speaking state, even when the portable radio device isheld by either of a left hand and a right hand, a high antenna gain canbe obtained.

Further, in the portable radio device according to the presentinvention, the switching portion switches whether the plurality of thefirst antenna elements are electrically connected to the feeding portionor electrically connected to the conductor element, respectively.

According to this structure, a diversity effect having a higherdirectivity is operationally obtained.

Further, in the portable radio device according to the presentinvention, a half-wavelength element electrically connected between atleast one of the plurality of the first antenna elements and theswitching portion is further provided.

According to this structure, even when the portable radio device isclosed, a high antenna performance is obtained.

Further, in the portable radio device according to the presentinvention, a plurality of half-wavelength elements respectivelyelectrically connected to the plurality of the first antenna elementsare further provided and the switching portion selectively switches theplurality of the first antenna elements and the plurality of thehalf-wavelength elements to connect them to the feeding portion.

According to this structure, even when the portable radio device isclosed, a high antenna performance can be obtained and a directionaldiversity effect can be also obtained.

Further, in the portable radio device according to the presentinvention, impedance matching portions respectively individuallycorresponding to the plurality of the first antenna elements are furtherprovided.

According to this structure, even when the portable radio device isclosed, the high antenna performance can be obtained.

Further, the portable radio device according to the present inventionfurther comprises: a casing opening and closing state detecting portionfor detecting whether or not the first casing and the second casing aremutually opened; and a control portion for controlling the switchingportion in accordance with the detected result of the casing opening andclosing state detecting portion.

According to this structure, a high antenna performance corresponding tothe opening or the closing state of the portable radio device can beobtained.

Further, in the portable radio device according to the presentinvention, a control portion is further provided for deciding thereceiving level of a radio circuit portion to control the switchingportion to raise the receiving level.

According to this structure, a high antenna performance can be alwaysensured under various using states of the portable radio device.

Further, in the portable radio device according to the presentinvention, the antenna element and the conductor element arerespectively formed in plate shapes along the surfaces of the firstcasing and the second casing.

According to this structure, the first antenna element and the conductorelement are respectively incorporated in the first casing and the secondcasing. However, the first casing and the second casing can berespectively formed with small thickness, so that they can sufficientlyoperationally meet a light and thin portable radio device.

Further, in the portable radio device according to the presentinvention, a circuit board formed in the second casing and having aradio circuit is further provided. The conductor element is formed in aground pattern formed on the circuit board disposed in the secondcasing. A ground of the radio circuit portion is electrically connectedto the ground pattern and the feeding portion is provided in the radiocircuit portion.

According to this structure, a high antenna performance can be ensuredand a thin portable radio device can be easily formed.

Further, the portable radio device according to the present inventionfurther comprises: a second antenna element provided in the secondcasing near the connection portion; an opening and closing statedetecting portion for detecting the opening and closing states of thefirst casing and the second casing; and a switching portion forselecting and switching any one of the first antenna element and thesecond antenna element to a connection to a signal processing portionfor performing a signal process. When the first casing and the secondcasing are opened, the first antenna element and the conductor elementform the dipole antenna, and when the first casing and the second casingare closed, the second antenna element and the conductor element form amono-pole antenna.

According to this structure, even when the first casing and the secondcasing are opened or closed, the high antenna performance can beassured.

Further, in the portable radio device according to the presentinvention, when the first casing and the second casing are opened, theswitching portion selects the first antenna element, and when the uppercasing and the lower casing are closed, the switching portion selectsthe second antenna element.

According to this structure, even when the upper casing and the lowercasing are opened or closed, the high antenna performance can beassured.

Further, the portable radio device according to the present inventionfurther comprises: a second antenna element provided in the secondcasing near the connection portion; a receiving field intensitymeasuring portion for measuring the receiving field intensity of asignal received by the first antenna element or the second antennaelement; and a switching portion for selecting and switching the antennaelement having a higher receiving field intensity to a connection to asignal processing portion for performing a signal process in accordancewith the measured result of the receiving field intensity measuringportion. The first antenna element has a first feeding point to beelectrically connected to the conductor element. The second antennaelement has a second feeding point to be electrically connected to theconductor element. The first feeding point and the second feeding pointare provided at the diagonal positions of opposed sides when the firstcasing and the second casing are opened.

According to this structure, a high antenna gain can be obtained eitherin a speaking sate by using a left hand or in a speaking state by usinga right hand.

Further, the portable radio device according to the present inventionfurther comprises: a first matching portion for matching the impedanceof the first antenna element to a prescribed value; and a secondmatching portion for matching the impedance of the second antennaelement to a prescribed value.

According to this structure, a high antenna performance can be ensured.

Further, the portable radio device according to the present inventionfurther comprises: a circuit board provided in the second casing; aplurality of feeding portions mutually separated from others for feedingelectric current to the antenna element; a radio circuit disposed in thecircuit board; and a switching portion provided between the plurality offeeding portions and the radio circuit to select and connect any one ofthe plurality of the feeding portions to the radio circuit.

According to this structure, a feeding position to the first antennaelement can be changed. Accordingly, since directivity can be changed, adirectional diversity effect can be obtained and a high antennaperformance can be obtained in a speaking state.

The portable radio device according to the present invention furthercomprises: a circuit board provided in the second casing; a radiocircuit disposed in the circuit board- and electrically connected to thefeeding portion; a ground portion spaced from the feeding portion toconnect the antenna element to the circuit board; and a switchingportion for switching whether the ground portion is connected to thecircuit board or the circuit board and the ground portion are opened.

According to this structure, whether or not a part of the first antennaelement separated from the feeding portion is grounded in the circuitboard can be switched. Accordingly, since directivity can be changed, adirectional diversity effect can be obtained and a high antennaperformance can be obtained in a speaking state.

Further, in the portable radio device according to the presentinvention, a plurality of ground portions are provided and the groundportions are disposed to be spaced apart in the end part of the antennaelement connected to the second casing.

According to this structure, since the directivity can be changed, thedirectional diversity effect can be obtained and the high antennaperformance can be obtained in a speaking state.

Further, in the portable radio device according to the presentinvention, the switching portion switches the ground portionsrespectively.

According to this structure, whether or not each part of the firstantenna element separated from the feeding portion is grounded in thecircuit board can be switched. Accordingly, since the directivity can bechanged, the directional diversity effect can be obtained and the highantenna performance can be obtained in a speaking state.

Further, in the portable radio device according to the presentinvention, the connection portion has an electric conductivity and theground portion is electrically connected to the antenna element throughthe connection portion.

According to this structure, the connection portion itself can serve asa feeder. Accordingly, a step for providing the feeder is not required,so that the number of assembling steps can be reduced and a cost can bedecreased.

Further, in the portable radio device according to the presentinvention, the connection portion has an electric conductivity and thefeeding portion is electrically connected to the antenna element throughthe connection portion.

Accordingly to this structure, the connection portion itself can serveas a feeder. Accordingly, a step for providing the feeder is notrequired, so that the number of assembling steps can be reduced and acost can be decreased.

Further, the portable radio device according to the present inventionfurther comprises: a control circuit for controlling the switchingportion in accordance with the level of a receiving signal received bythe radio circuit.

According to this structure, the feeding portion or the ground portionis switched in accordance with the level of the receiving signal.Accordingly, even when the portable radio device is held by either aleft hand or a right hand in a speaking state, a high antennaperformance can be obtained.

Further, in the portable radio device according to the presentinvention, the first antenna element is an electric conductive frameforming a part of the first casing.

According to this structure, since the electric conductive frame forminga part of the upper casing is used as the antenna element, the thicknessof the portable radio device can be decreased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of a portable radio device in afirst embodiment of the present invention;

FIGS. 2A and 2B are diagrams showing the directivity of an antenna ofthe portable radio device according to the first embodiment;

FIGS. 3A and 3B are explanatory views for explaining using states of theportable radio device according to the first embodiment;

FIGS. 4A and 4B are diagrams showing the directivity of the antennaunder a state in which the portable radio device according to the firstembodiment is inclined by 60 degrees;

FIG. 5 is a schematic structural diagram of a portable radio device in asecond embodiment of the present invention;

FIGS. 6A and 6B are diagrams showing the directivity of an antenna ofthe portable radio device according to the second embodiment;

FIG. 7 is a schematic structural diagram of a portable radio device in athird embodiment of the present invention;

FIG. 8 is an explanatory view showing the operation of a closing state(first) of the portable radio device according to the third embodiment;

FIG. 9 is an explanatory view showing the operation of a closing state(second) of the portable radio device according to the third embodiment;

FIGS. 10A and 10B are diagrams showing the directivity of an antenna ofthe portable radio device according to the third embodiment;

FIG. 11 is a schematic structural diagram of a portable radio device ina fourth embodiment of the present invention;

FIG. 12 is a schematic structural diagram of a portable radio device ina fifth embodiment of the present invention;

FIG. 13 is a schematic structural diagram of a portable radio device ina sixth embodiment of the present invention;

FIG. 14 is a front view showing a portable radio device in a seventhembodiment;

FIG. 15 is a side view showing the portable radio device of the seventhembodiment;

FIG. 16 is an explanatory view showing a state that the portable radiodevice of the seventh embodiment is held by a left hand at aninclination angle of 60 degrees;

FIG. 17 is an explanatory view showing the operation of an antenna whena first antenna element is selected while the portable radio device ofthe seventh embodiment is in a left hand speaking state;

FIG. 18 is an explanatory view showing directivity when the firstantenna element is selected while the portable radio device of theseventh embodiment is in a left hand speaking state;

FIG. 19 is an explanatory view showing the operation of an antenna whena second antenna element is selected while the portable radio device ofthe seventh embodiment is in a left hand speaking state;

FIG. 20 is an explanatory view showing directivity when the secondantenna element is selected while the portable radio device of theseventh embodiment is in a left hand speaking state;

FIG. 21 is an explanatory view showing a state that the portable radiodevice of the seventh embodiment is held by a right hand at aninclination angle of 60 degrees;

FIG. 22 is an explanatory view showing the operation of an antenna whena first antenna element is selected while the portable radio device ofthe seventh embodiment is in a right hand speaking state;

FIG. 23 is an explanatory view showing directivity when the firstantenna element is selected while the portable radio device of theseventh embodiment is in a right hand speaking state;

FIG. 24 is an explanatory view showing the operation of an antenna whena second antenna element is selected while the portable radio device ofthe seventh embodiment is in a right hand speaking state;

FIG. 25 is an explanatory view showing directivity when the secondantenna element is selected while the portable radio device of theseventh embodiment is in a right hand speaking state;

FIG. 26 is a front view showing a portable radio device for explainingan eighth embodiment;

FIG. 27 is a diagram for explaining the operation of an antenna of theportable radio device according to the eighth embodiment;

FIG. 28 is a diagram showing the directivity of the antenna of theportable radio device according to the eighth embodiment;

FIG. 29 is a diagram showing a speaking state that a user holds theportable radio device according to the eighth embodiment by a left hand;

FIG. 30 is a diagram for explaining the operation of the antenna of theportable radio device according to the eighth embodiment;

FIG. 31 is a diagram showing the directivity of the antenna of theportable radio device according to the eighth embodiment;

FIG. 32 is a diagram showing a speaking state that a user holds theportable radio device according to the eighth embodiment by a righthand;

FIG. 33 is a front view showing a portable radio device for explaining aninth embodiment;

FIG. 34 is a side view showing the portable radio device for explainingthe ninth embodiment of the present invention;

FIG. 35 is a front view showing a portable radio device for explaining atenth embodiment of the present invention;

FIG. 36 is a diagram showing the directivity of an antenna of theportable radio device according to the tenth embodiment of the presentinvention; and

FIG. 37 is a diagram showing the directivity of the antenna of theportable radio device according to the tenth embodiment of the presentinvention.

In the drawings, reference numerals 1, 104 and 210 designate uppercases, 2, 105 and 211 designate lower cases, 3, 106, 212 a, 212 b and212 c designate hinge portions, 4 designates a plate shaped conductor, 5designates a plate shaped conductor, 6 designates a ground plate, 7designates a speaker, 8 designates an operating key, 9 designates amicrophone, 10,11,34, 35, 108 and 113 designate feeding points, 12 and13 designate feeders, 14, 24, 25, 31, 33 and 36 designate high frequencyswitches, 15 designates a feeding portion, 30 and 32 designate helicalelements, 37, 38, 110 and 114 designate matching circuits, 39 designatesa control portion, 40 designates a magnet switch, 41 designates apermanent magnet, 42 designates a printed circuit board, 43 designates aground pattern, 44, 112 and 224 designate radio circuit portions, 45designates a level deciding portion, 101 and 102 designate antennaelements, 103 and 221 designate circuit boards, 111 designates a highfrequency switch, 127 designates a switch control portion, 128designates an opening and closing detecting portion, 203 and 204designate feeding portions, 205, 206, 222 a, 222 b and 228 designatematching circuits, 213 designates a sound port, 214 designates a metalframe, 215 a, 15 b, 15 c, 19 a, 19 b and 19 c designate hinge fittings,216 and 229 designate attaching screws, 217 and 226 designate tappedhole parts, 218 a, 218 b and 218 c designate rotating shafts, 220 a, 220b and 220 c designate feeding terminals, 223, 227 a and 227 b designateswitches and 225 designates a control circuit portion.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

FIG. 1 is a schematic structural diagram of a portable radio device in afirst embodiment of the present invention. The portable radio device inthis embodiment is a portable radio device having a foldable structureand is shown in an opened state (refer this state as to an openingstate, hereinafter) in FIG. 1. The portable radio device includes anupper case 1, a lower case 2, a hinge portion 3, a plate shapedconductor 4, a plate shaped conductor 5, a ground plate 6, a speaker 7,an operating key 8 and a microphone 9.

The upper case 1 and the lower case 2 as one example of a first casingand a second casing are formed with a resin as an insulator andordinarily set to the length of about 10 mm and the width of about 50mm. The upper case 1 and the lower case 2 are respectively connected inthe hinge portion 3 so as to freely rotate. Thus; a foldable or acollapsible structure is formed.

In the upper end part of the upper case 1, the speaker 7 is disposed. Inthe lower end part of the lower case 2, the microphone 9 is disposedrespectively. In a speaking state that a user holds the portable radiodevice by a hand to speak, the user can use the portable radio device byallowing the speaker 7 to come near to the ear and the microphone 9 tocome near to the mouth respectively.

The plate shaped conductors 4 and 5 as one example of a first antennaelement are made of a copper plate having, for instance, the length L1of about 90 mm and the width L2 of about 15 mm. The plate shapedconductors 4 and 5 are disposed along the surface of the upper case 1 inthe inner part of the upper case 1. Further, the thickness of the plateshaped conductors 4 and 5 is set to, for instance, about 0.1 mm. Theplate shaped conductors 4 and 5 are disposed so as not to structurallyinterfere with other components such as the speaker 7 or a displayelement in the inner part of the upper case 1 having the thickness asthin as, for instance, about 6 mm.

The ground plate 6 as one example of a conductor element is made of, forinstance, a conductor plate having the length L3 of about 90 mm and thewidth L4 of about 45 mm. The ground plate may use a ground pattern of acircuit board disposed in the lower case 2. The ground plate 6 whosethickness is set to 1 mm or smaller is disposed so as not tostructurally interfere with other components such as the operating key 8or the microphone 9 in the lower case 2.

A feeding point 10 and a feeding point 11 provided in the lower parts ofthe plate shaped conductor 4 and the plate shaped conductor 5 areelectrically connected to a high frequency switch 14 by a feeder 12 anda feeder 13. As the feeder 12 and the feeder 13, a flexible wire rodthat can be freely bent is used. Thus, the upper case 1 can rotate inthe hinge portion 3.

The high frequency switch 14 is formed by, for instance, an FET or a PINdiode to suitably select the high frequency signals of the feeder 12 andthe feeder 13 (suitably select a larger one of the high frequencysignals on the basis of, for instance, the directions of the cases 1 and2 or the magnitude of the high frequency signals of the feeders 12 and13) to transmit the high frequency signal to one end of a feedingportion 15. The feeding portion 15 is an antenna feeding portion of atransmitting and receiving circuit disposed in the lower case 2. Theother end of the feeding portion 15 is grounded in the ground plate 6.

In the portable radio device constructed as described above, anoperation of an antenna when radio frequency is set to, for instance,900 MHz (wavelength is about 333 mm) is described below as an example.

In the high frequency switch 14, when an A side terminal is selected,the plate shaped conductor 4 is selected. In this case, the plate shapedconductor 4 and the ground plate 6 operate as, for instance, a dipoleantenna of half-wavelength. Further, when the high frequency switch 14selects a B side terminal, the plate shaped conductor 5 and the groundplate 6 likewise operate as, for instance, a dipole antenna of, abouthalf-wavelength. Accordingly, the plate shaped conductors 4 and 5 andthe ground plate 6 operate as the dipole antenna provided in the uppercase 1 and the lower case 2 of the portable radio device.

The antenna current of the dipole antenna constructed as described aboveis distributed over a wide range from the upper ends of the plate shapedconductors 4 and 5 and the lower end of the ground plate 6. Accordingly,for instance, when the user holds only the lower case 2 by the hand, orwhen the user holds only the hinge portion 3 by the hand, thedeterioration of an antenna gain is suppressed to a minimum. This arisesbecause of a reason why the antenna current is distributed throughout awide range from the upper end of the upper case 1 to the lower end ofthe lower case 2. Thus, even when the antenna current of a specific partis influenced by the hand, the influence given to the operation of allthe antenna is low.

FIGS. 2A and 2B are diagrams showing the directivity of the dipoleantenna shown in FIG. 1. In FIG. 2A, the directivity 16 and thedirectivity 17 respectively show the directivities of Eθ (verticallypolarized wave) components on an XY plane. Further, in FIG. 2B, thedirectivity 18 and the directivity 19 respectively show thedirectivities of Eθ components on a YZ plane.

Further, the directivity 16 and the directivity 18 show thedirectivities of a state that the A side of the high frequency switch 14in FIG. 1 is selected, that is, the plate shaped conductor 4 isselected. Further, the directivity 17 and the directivity 19 show thedirectivities of a state that the B side of the high frequency switch 14is selected, that is, the plate shaped conductor 5 is selected.

As apparent from FIGS. 2A and 2B, when the plate shaped conductor 4 isselected, a gain in the direction of Y is high. When the plate shapedconductor 5 is selected, the gain in the direction of −Y is high. Asdescribed above, when the plate shaped conductor 4 or the plate shapedconductor 5 having a higher gain is automatically selected by the highfrequency switch 14, a directional diversity effect can be obtained.

Now, the antenna gain under a state that the portable radio device in aspeaking state will be described below. FIGS. 3A and 3B are diagramsshowing speaking states that the user holds the portable radio device bya left hand or a right hand to allow the device to come near to the earor the mouth for speaking. As shown in FIGS. 3A and 3B, under thespeaking state, the portably radio device is frequently inclined byabout 60 degrees from a direction of Z. Further, the hand by which theuser holds the portable radio device cannot be frequently limited to theleft hand or the right hand. Accordingly, under both the states shown inFIGS. 3A and 3B, the high antenna gain is required for the portableradio device.

In a land mobile telecommunication system like a portable telephonesystem, it has been know that a radio wave coming to the portable radiodevice from a radio base station has an elevation angle θ of 90 degreesin coordinate systems shown in FIGS. 3A and 3B, that is, the radio waveis concentrated in the direction of a horizontal plane (XY plane).Accordingly, the high antenna gain in the direction of the horizontalplane is required for the antenna for the portable radio device underboth the states shown in FIGS. 3A and 3B.

FIGS. 4A and 4B respectively show directivities on an XZ plane under astate that the portable radio device shown in FIG. 1 is disposed to beinclined by 60 degrees, that is, when the portable radio device islocated in the speaking states shown in FIGS. 3A and 3B. Coordinatesystems shown in FIGS. 4A and 4B respectively correspond to thecoordinate systems shown in FIGS. 3 a and 3B.

In FIG. 4A, the directivity 20 and the directivity 21 respectively showthe directivities of Eθ (vertically polarized wave) components on the XZplane when the portable radio device is held by the left hand. Further,in FIG. 4B, the directivity 22 and the directivity 23 respectively showthe directivities of Eθ (vertically polarized wave) components on the XZplane when the portable radio device is held by the right hand.

Further, the directivity 20 and the directivity 22 show thedirectivities of a state that the A side of the high frequency switch 14in FIG. 1 is selected, that is, the plate shaped conductor 4 isselected. Further, the directivity 21 and the directivity 23 show thedirectivities of a state that the B side of the high frequency switch 14is selected, that is, the plate shaped conductor 5 is selected.

As apparent from FIGS. 4A and 4B, when the portable radio device is heldby the left hand, the directivity 21 of the state that the plate shapedconductor 5 is selected has a higher gain on the XZ plane. Further, whenthe portable radio device is held by the right hand, the directivity 22of the state that the plate shaped conductor 4 is selected has a highergain on the XZ plane.

As described above, when the right hand and the left hand respectivelyhold the portable radio device, the different plate shaped conductors 4and 5 respectively have higher gains. In this embodiment, thisphenomenon is employed to provide, for instance, a detecting unit, whichis not shown in the drawings, for automatically detecting the directionsof the cases 1 and 2, that is, whether the portable radio device is heldby the right hand or the left hand. A switching unit is provided forautomatically switching the high frequency switch 14 shown in FIG. 1 tothe higher gain in accordance with the directions of the cases 1 and 2detected by the detecting unit. Thus, the high antenna gain can beobtained in any of the speaking states that the portable radio device isheld by the left hand or the right hand. Further, a measuring unit formeasuring the respective gains of the plate shaped conductors 4 and 5and a switching unit for automatically switching the switch to thehigher gain on the basis of the gains measured by the measuring unit maybe provided, so that the high antenna gain can be obtained in any of thespeaking states that the portable radio device is held by the left handor the right hand.

In this embodiment, the two plate shaped conductors are incorporated inthe upper case 1 to switch them. However, a single plate shapedconductor may be provided in the upper case. Also in this case, theantenna gain in a speaking state can be improved.

The form of the plate shaped conductor contained in the upper case 1 isnot limited to the form shown in this embodiment. A structure operatingtogether with the ground plate contained in the lower case 2 as a dipoleantenna of, for instance, about half-wavelength may obtain the sameeffects.

The plate shaped conductors contained in the upper case 1 may berespectively formed with a conductor for supporting, for instance, aliquid crystal display in view of a mechanism, or the plate shapedconductor may be respectively formed with a conductor thin film stuck tothe surface of a resin of the upper case 1 or a conductor thin filmembedded in the resin.

Further, in order to reduce an influence that the portable radio deviceis allowed to come near to the head part of a user, particularly to theear under a speaking state, the plate shaped conductors incorporated inthe upper case 1 are desirably arranged at positions-separate from thesurface of the upper case on which the speaker 7 is disposed, that is,at positions near a surface opposed to the surface on which the speaker7 is disposed as much as possible.

Second Embodiment

FIG. 5 is a schematic structural diagram of a portable radio device in asecond embodiment of the present invention. The portable radio device inthis embodiment is also a portable radio device having a foldable orcollapsible structure. In FIG. 5, an opened state (refer this state toas an opening state, hereinafter) is shown. In FIG. 5, duplicatedportions of FIG. 1 are designated by the same reference numerals.

In the portable radio device shown in FIG. 5, the plate shaped conductor4 or the plate shaped conductor 5 that is not selected is grounded in aground plate 6.

In FIG. 5, feeders 12 and 13 are respectively connected to highfrequency switches 24 and 25. The high frequency switch 24 performs anoperation for switching whether an electric signal of the feeder 12 istransmitted to a feeding portion 15 or grounded to the ground plate 6.Further, the high frequency switch 25 performs an operation forswitching whether an electric signal of the feeder 13 is transmitted tothe feeding portion 15 or grounded in the ground plate 6.

Here, for instance, when a terminal B1 side of the high frequency switch25 is selected and the plate shaped conductor 5 is connected to thefeeding portion 15, a terminal A2 side of the high frequency switch 24is selected and the plate shaped conductor 4 is grounded in the groundplate 6. On the contrary, when a terminal A1 side of the high frequencyswitch 24 is selected and the plate shaped conductor 4 is connected tothe feeding portion 15, a terminal B2 side of the high frequency switch25 is selected and the plate shaped conductor 5 is grounded in theground plate 6.

FIGS. 6A and 6B show directivities when the high frequency switches areoperated as described above. In FIG. 6A, the directivity 26 and thedirectivity 27 respectively show the directivities of Eθ (verticallypolarized wave) components on an XY plane. In FIG. 6B, the directivity28 and the directivity 29 respectively show the directivities of Eθcomponents on a YZ plane.

Further, the directivity 26 and the directivity 28 show thedirectivities of a state that the terminal A1 side of the high frequencyswitch 24 and the terminal B2 side of the high frequency switch 25 inFIG. 5 are selected, that is, the directivities of a state that anelectric current is supplied to the plate shaped conductor 4 and theplate shaped conductor 5 is grounded in the ground plate 6. Further, thedirectivity 27 and the directivity 29 show the directivities of a statethat an electric current is supplied to the plate shaped conductor 5 andthe plate shaped conductor 4 is grounded in the ground plate 6.

As apparent from FIGS. 6A and 6B, when the plate shaped conductor 4 isturned on, a gain in the direction of Y is high. When the plate shapedconductor 5 is turned on, the gain in the direction of −Y is high. Thistendency is the same as the tendency shown in FIG. 2. However, an amountof variation of a maximum gain in FIG. 6 is apparently higher than thatof FIG. 2. This arises because of a reason why the plate shapedconductor that is not turned on is grounded in the ground plate 6 sothat these members operate as a reflecting element. As described above,a directional diversity effect obtained by the structure shown in FIG. 5is higher than that obtained by the structure shown in FIG. 1.

The structures of the high frequency switch 24 and the high frequencyswitch 25 are not limited to the structure shown in this embodiment. Anyof structures that can switch whether the plate shaped conductor isturned on or grounded in the ground plate may obtain the same effects.

Third Embodiment

FIG. 7 is a schematic structural diagram of a portable radio deviceaccording to a third embodiment of the present invention. The portableradio device in this embodiment is also a portable radio device having afoldable or collapsible structure. In FIG. 7, an opened state (referthis state to as an opening state, hereinafter) is shown. In FIG. 7, theduplicated portions of FIG. 1 are designated by the same referencenumerals.

In FIG. 7, a helical element 30 is inserted between a plate shapedconductor 5 and a high frequency switch 31.

In FIG. 7, the helical element 30 is formed by winding a conductor in acoil shape. The electric length thereof is preferably set tosubstantially half-wavelength in an operating frequency (for instance,900 MHz). In this case, the helical element 30 is inserted between theplate shaped conductor 5 and the high frequency switch 31, so that aphase for exciting the plate shaped conductor 5 is inverted.

FIGS. 8 and 9 are side views of the portable radio device shown in FIG.7 and show states that an upper case 1 and a lower case 2 are closed(refer this state to as a closing state, hereinafter). FIG. 8 shows astate that a terminal A1 side of the high frequency switch 31 shown inFIG. 7 is selected, that is, a plate shaped conductor 4 is selected.FIG. 9 shows a state that a terminal A2 side of the high frequencyswitch 31 shown in FIG. 7 is selected, that is, the plate shapedconductor 5 is selected.

In the state shown in FIG. 8, the phases of antenna currents distributedin the plate shaped conductor 4 and a ground plate 6 are shown by arrowmarks. Accordingly, the antenna currents on the plate shaped conductor 4and the ground plate 6 are respectively cancelled to each other so thata radiation resistance is extremely lowered. Thus, the radiationefficiency of an antenna is lowered to increase a loss in non-matchingof impedance. As a result, an antenna gain of this state is decreased toreduce a bandwidth.

As compared therewith, in the state that the terminal A2 side of thehigh frequency switch 31 as shown in FIG. 9 is selected, that is, in thestate that the helical element 30 and the plate shaped conductor 5 areselected, the phases of antenna currents distributed on the plate shapedconductor 5 and the ground plate 6 correspond to each other.

FIGS. 10A and 10B show the directivities of Eθ components of the stateshown in FIG. 9 on an XY plane and an XZ plane. As apparent from FIG.10A and FIG. 10B, the Eθ components substantially have no directivitieson a horizontal plane (XY plane) and have 8-shaped directivities on theXZ plane. Under this state, a high antenna gain and a wide bandwidth canbe assured.

In such a way, when the portable radio device is in the opening state,the high frequency switch 31 is switched to the terminal A1 side. Whenthe portable radio device is in the closing state, the high frequencyswitch 31 is switched to the terminal A2 side. Thus, an antennaperformance can be obtained in both the states.

Any of the helical elements 30 whose electric length has substantiallyhalf-wavelength may have the same effects. For instance, a meanderpattern printed on a printed circuit board or an insulator may beemployed. Further, the helical element 30 may be formed with a meanderconductor as a part of the plate shaped conductor 5.

Fourth Embodiment

FIG. 11 is a schematic structural diagram of a portable radio device ina fourth embodiment of the present invention. The portable radio deviceof this embodiment is also a portable radio device having a foldable orcollapsible structure. FIG. 11 shows an opened state (refer this stateto as an opening state, hereinafter). In FIG. 11, duplicated portions tothose of FIG. 7 are designated by the same reference numerals.

In the portable radio device shown in FIG. 11, a helical element 32 isinserted between a feeding point 34 of a plate shaped conductor 4 and ahigh frequency switch 33 and a feeding point 11 of a plate shapedconductor 5 is connected to the high frequency switch 33.

In FIG. 11, the helical element 32 has the same electric characteristicsas those of a helical element 30. A high frequency switch 31 and thehigh frequency switch 33 are selected by a high frequency switch 36 tosupply electric current to a feeding portion 15.

In the above-described structure, under a state that a terminal A1 sideof the high frequency switch 31 and a terminal B1 side of the highfrequency switch 33 are selected, the plate shaped conductor 4 or theplate shaped conductor 5 and a ground plate 6 operate as a dipoleantenna having the same structure shown in FIG. 1 which is formed by theplate shaped conductor 4 or the plate shaped conductor 5 and the groundplate 6. In the opening state, this state is desirably selected. In thatcase, a high antenna gain can be obtained. Then, at this time, the plateshaped conductor 4 or the plate shaped conductor 5 is selected by thehigh frequency switch 36 so that a directional diversity effect isobtained.

Then, under a closing state, a terminal A2 side of the high frequencyswitch 31 and a B2 side of the high frequency switch 33 are desirablyselected. In this state, an antenna operation similar to that of thestructure shown in FIG. 9 is achieved so that the high antenna gain canbe obtained under the closing state. At this time, the plate shapedconductor 4 or the plate shaped conductor 5 is selected by the highfrequency switch 36 so that a directional diversity effect under theclosing state can be obtained.

Fifth Embodiment

FIG. 12 is a schematic structural diagram of a portable radio device ina fourth embodiment of the present invention. The portable radio deviceof this embodiment is also a portable radio device having a foldable orcollapsible structure. FIG. 12 shows an opened state (refer this stateto as an opening state, hereinafter). In FIG. 12, duplicated portions tothose of FIG. 7 are designated by the same reference numerals.

In the portable radio device shown in FIG. 12, a matching circuit 37 anda matching circuit 38 are provided. When a plate shaped conductor 4 isselected in the opening state, or when a plate shaped conductor 5 isselected in a closing state, a suitable impedance matching is performedfor both the cases.

Further, in the portable radio device shown in FIG. 12, a controlportion 39, a magnet switch 40 and a permanent magnet 41 are added todetect the opening state or the closing state of the portable radiodevice and switch a high frequency switch 31 in accordance therewith.

In FIG. 12, the matching circuit 37 and the matching circuit 38 areformed with, for instance, concentrated constant elements such asinductance and condensers. The matching circuit 37 operates so that theimpedance of a dipole antenna formed by the plate shaped conductor 4 inthe opening state and a ground plate 6 is matched with the impedance(ordinarily, 50Ω) of a feeding portion 15. Further, the matching circuit38 operates so that the impedance of an antenna formed by the plateshaped conductor 5 in the closing state, a helical element 30 and theground plate 6 is matched with the impedance of the feeding portion 15.

As described above, the suitable matching circuits are providedrespectively for the plate shaped conductors or the opening and closingstates. Thus, an antenna performance for each of the states is moreimproved.

Then, for instance, in the closing state, since the magnet switch 40comes near to the permanent magnet 41, the magnet switch 40 is turnedON. The control portion 39 detects this state and operates to switch thehigh frequency switch 31 to a terminal B side. On the other hand, in theopening state, the magnet switch 40 is turned OFF to switch the highfrequency switch 31 to a terminal A side.

In such a way, suitable antenna states are selected in accordance withthe detected results of the opening and closing states, so that a highantenna gain can be obtained for both the states.

The matching circuit is not limited to a circuit composed of theconcentrated constant elements and may be formed by, for instance, aplane circuit disposed on a printed circuit board. Further, means fordetecting the opening and closing states is not limited to the magnetswitch and the permanent magnet. For instance, means for detecting anoperation of a mechanism of a hinge portion may be employed, or meansinterlocking with an operating state such as a speaking mode or awaiting mode of the portable radio device may be employed.

Sixth Embodiment

FIG. 13 is a schematic structural diagram of a portable radio device ina sixth embodiment of the present invention. The portable radio deviceof this embodiment is also a portable radio device having a foldable orcollapsible structure. FIG. 13 shows an opened state (refer this stateto as an opening state, hereinafter). In FIG. 13, duplicated portions tothose of FIG. 7 or FIG. 12 are designated by the same referencenumerals.

In the portable radio device shown in FIG. 13, the ground plate 6 in theportable radio device shown in FIG. 7 is formed with a ground pattern 43on a printed circuit board 42. A radio circuit portion 44 and a leveldeciding portion 45 mounted on the printed circuit board 42 are added.

In FIG. 13, as the printed circuit board 42, for instance, a glass epoxybase having the thickness of about 1 mm is used. The ground pattern 43is formed with a silver foil pattern printed on the surface or the innerlayer of the printed circuit board 42. The ground pattern 43 functionsas an antenna in the same manner as that of the ground plate 6 in FIG.7. Such a structure is provided so that the ground plate operating asthe antenna does not need to be overlaid on the printed circuit board 42as an originally necessary component. Thus, the decrease of thickness ofa lower case 2 of the portable radio device can be realized.

The radio circuit portion 44 is composed of a transmitting circuit and areceiving circuit and covered with electromagnetic shielding means suchas a shield case. A signal selected by a high frequency switch 31 istransmitted to the radio circuit portion 44 and the ground of the radiocircuit portion 44 is grounded in the ground pattern 43. In accordancewith such a structure, to an antenna formed by plate shaped conductors 4and 5 and the ground pattern 43, electric current is fed by the radiocircuit portion 44.

The level deciding portion 45 includes a function for deciding whether areceiving level obtained in the receiving circuit that forms the radiocircuit portion 44 is high or low and a function for switching the highfrequency switch 31 in accordance therewith. Specifically, the leveldetermining portion 45 determines the receiving levels respectivelyobtained when the high frequency switch 31 is switched to a terminal Aside or a terminal B side and operates to select the terminal side of ahigher receiving level. For instance, when the portable radio device ofthis embodiment is applied to a time division multiplex connection(TDMA) system, a series of operations as described above arecontinuously carried out at a suitable timing. Accordingly, a highantenna gain can be always ensured.

Seventh Embodiment

FIG. 14 is a front view showing a portable radio device for explaining aseventh embodiment of the present invention. FIG. 15 is a side viewshowing the portable radio device for explaining the seventh embodimentof the present invention. As shown in these figures, the portable radiodevice of this embodiment is a foldable or collapsible radio device inwhich an upper case 104 and a lower case 105 are connected together by ahinge portion 106. The upper case and the lower case are rotated on thehinge portion 106 so that two states including an opening state and aclosing state may be obtained. The upper case 104 and the lower case 105are made of molded products of a resin as an insulator.

In the upper case 104, an antenna element 101 and a speaker 107 having asound generating element are provided. The antenna element 101 is formedwith a plate shaped conductor base. However, the antenna element 101 isnot limited to the plate shaped conductor base. For instance, a groundpattern of a circuit board provided in the upper case 104 or a metallicframe for mechanically supporting the speaker 107 may be employed, or ametallic plate forming the upper case 104 itself may be employed.Further, the speaker 107 is used when a user listens to a sound uponspeaking. A sound hole surface for emitting sound is directed to thedirection of X in a coordinate system shown in FIG. 14. The user allowshis ear to come into contact with a part near the speaker 107 on an Xside surface outside the upper case 104 to speak.

Further, in the lower case 105, an antenna element 102 as an example ofa second antenna element and a circuit board 103 as an example of aconductor element are provided. The antenna element 102 is an L-shapedconductor plate and a long side part thereof is arranged along a Y-axisdirection in the vicinity of the hinge portion 106 in the lower case105. The long side of the antenna element 102 has a length of about ¼ to½ wavelength relative to a radio signal.

The circuit board 103 is a printed circuit board on which circuits forrealizing a radio communication function or various kinds of otherfunctions are mounted. A ground pattern serving as an earth potential ofthe circuits is formed on a substantially entire surface thereof.Further, the circuit board 103 includes a matching circuit 110 as oneexample of a first matching portion, a matching circuit 114 as oneexample of a second matching portion, a high frequency switch 111 and aswitch control portion 127 as one example of a switching portion, aradio circuit portion 112 as one example of a receiving field intensitymeasuring portion and a signal processing portion, and an opening andclosing detecting portion 128 as one example of an opening and closingdetecting portion.

The matching circuit 110 serves to match the impedance of the antennaelement 101 with, for instance, 50Ω and is connected to the antennaelement 101 at a feeding point 108 through a feeder 109. The matchingcircuit 110 is arranged at a position near the right side (Y) of thecircuit board 103. The feeding point 108 is arranged at a position nearthe right side (Y) by viewing the portable radio device from a frontsurface (X) side on the antenna element 101.

Further, the matching circuit 114 serves to match the impedance of theantenna element 102 with, for instance, 50Ω and is connected to theantenna element 102 at a feeding point 113 through a feeder. Thematching circuit 114 is arranged at a position near the left side (−Y)on the circuit board 103, that is, a side opposed the matching circuit110. The feeding point 113 is arranged at a position near the left side(−Y) by viewing the portable radio device from a front surface (X) sideon the antenna element 102, that is. A side opposed to the feeding point108.

The high frequency switch 111 is composed of an FET or a PIN diode orthe like to select either the matching circuit 110 or the matchingcircuit 114 and transmit a signal received by the antenna element 101 orthe antenna element 102 to the radio circuit portion 112. The radiocircuit portion 112 performs a signal process to a transmitted signal ora received signal, and especially measures the receiving field intensityof the signal received by the antenna element 101 or the antenna element102. Further, the opening and closing detecting portion 128 serves todetect the opening and closing states of the upper case 104 and thelower case 105 and is realized by for instance, a permanent magnet, aHall element and a mechanical switch or the like.

The switch control portion 127 serves to control the high frequencyswitch 111 to select the antenna element having a higher receivingintensity in accordance with the detected result of the opening andclosing detecting portion 128 or the receiving field intensity of eachof the antenna elements 101 and 102 measured by the radio circuitportion 112. Owing to a below-described reason, the switch controlportion 127 selects the antenna element 101 side under the opening stateand selects the antenna element 102 side under the closing state.

An antenna operation in the portable radio device of the seventhembodiment having the above-described components will be describedbelow. In the following description, it is assumed that radio frequencyis 1.5 GHz (wavelength of 200 mm) is used.

Initially, the antenna operation under a state in which the upper case104 and the lower case 105 are opened as shown in FIG. 14 will bedescribed. Under this state, when the matching circuit 110 side, thatis, the antenna element 101 side is selected by the high frequencyswitch 111, the antenna element 101 and the circuit board 103 arearranged in a straight line. Thus, these members serve as a dipoleantenna of one wavelength. On the other hand, when the matching circuit113 side, that is, the antenna element 102 side is selected, the antennaelement 102 feeds unbalanced electric current to the circuit board 103through the feeding point 113 and further operates while the antennaelement 102 is electro-magnetically connected to the antenna element101. In such a way, under the opening state, even when either of theantenna elements is selected, a high antenna performance is obtained.

Then, the antenna operation when the upper case 104 and the lower case105 are closed is described below. Under this state, when the antennaelement 101 side is selected by the high frequency switch 111, theantenna element 101 comes near to the circuit board 103. Thus, antennacurrents have opposite phases to be cancelled to each other, so that anantenna performance is deteriorated. On the other hand, when the antennaelement 102 side is selected by the high frequency switch 111, theantenna element 102 operates as a mono-pole antenna of ¼ wavelength forfeeding unbalanced electric current to the circuit board 103 through thefeeding point 113. Accordingly, the antenna performance higher than thatwhen the antenna element 101 is selected is obtained. In such a way,under the closing state, when the antenna element 102 side is selected,a higher antenna performance can be obtained.

Now, an antenna operation under a state that the user holds the portableradio device of this embodiment by a left hand to speak will bedescribed below. FIG. 16 to FIG. 20 are explanatory views showingantenna operations and directivities when the portable radio device ofthis embodiment is held by a left hand (a left hand speaking state). Anaverage inclination angle α at which the user holds the portable radiodevice under the speaking state is ordinarily 60 degrees. FIG. 16 is anexplanatory view showing a state that the portable radio device of thisembodiment is held by the left hand at the inclination angle of 60degrees.

As shown in FIG. 17, when the antenna element 101 side is selected bythe high frequency switch 111, since the lower case 105 is held by thehand, the radiation of radio wave from the circuit board 103 provided inthe lower case 105 is decreased and the radiation from electric current115 on the antenna element 101 has a control. As a result, a mainpolarized wave component on a horizontal plane (XY plane) becomes ahorizontal (Eφ) component. Accordingly, as shown in FIG. 18, in thedirectivity on the horizontal plane (XY plane), the directivity 120 of ahorizontally polarized wave (Eφ) component is higher in the direction ofa Y side (left hand side) than the directivity 119 of a verticallypolarized wave (Eθ).

On the other hand, as shown in FIG. 19, when the antenna element 102side is selected by the high frequency switch 111, the radiation from anelectric current 118 due to a vector synthesis of an electric current116 on the antenna element 102 and an electric current 117 on theantenna element 101 electro-magnetically connected to the electriccurrent 116 has a control. As a result, the vertically polarized wave(Eθ) component on the horizontal (XY) plane is higher than that when theantenna element 101 is selected. Accordingly, as shown in FIG. 20, inthe directivity on the horizontal (XY) plane, the directivity 121 of thevertically polarized wave (Eθ) is higher in the direction of the Y side(left hand side) than the directivity 122 of the horizontally polarizedwave (Eφ) component.

Generally, as an index showing the effective antenna performance of theportable radio device under a speaking state, a pattern average gain(PAG) expressed by a below-described formula (1) is employed. In theformula (1), G_(θ) (φ) and G_(φ) (φ) respectively indicate powerdirectivities on the horizontal plane (XY plane) of the verticallypolarized wave component and the horizontally polarized wave. Further,C_(VH) indicates a correction factor related to the cross polarizationpower ratio (a power ratio of the vertically polarized wave component tothe horizontally polarized wave component) of an arriving wave inputtedto an antenna.

$\begin{matrix}{{PAG} = {\frac{1}{2\pi}{\int_{0}^{2\pi}{\left\lbrack {{G_{\theta}\left( {\frac{\pi}{2},\phi} \right)} + {\frac{1}{C_{VH}}{G_{\phi}\left( {\frac{\pi}{2},\phi} \right)}}} \right\rbrack\ {\mathbb{d}\phi}}}}} & (1)\end{matrix}$

It is known that the ordinary cross polarization power ratio in themulti-wave environment of a land mobile telecommunication is 4 to 9 dB.This indicates that the electric power of the vertically polarized waveof the arriving wave is higher by 4 to 9 dB than the electric power ofthe horizontally polarized wave. Accordingly, the formula (1) means thatthe vertically polarized wave is weighted and the power directivities onthe horizontal plane are averaged. C_(VH) is explained as 9 dB,hereinafter. Therefore, in the antenna for the portable radio device,the vertically polarized wave component is increased in a using state toobtain the high pattern average gain (PAG).

The PAG is used to show radiation characteristics in FIG. 18 and FIG.20. The PAG obtained when the antenna element 101 is selected is −15 dBd(dipole ratio gain). On the other hand, the PAG obtained when theantenna element 102 is selected is −11.5 dBd, which is higher by 3.5 dBthan the former. Accordingly, in the left hand speaking state, when theantenna element 102 is selected, the PAG becomes higher.

Now, an antenna operation under a state that the user holds the portableradio device of this embodiment by a right hand to speak will bedescribed below. FIG. 21 to FIG. 25 are explanatory views showingantenna characteristics and directivities when the portable radio deviceof this embodiment is held by a right hand (a right hand speakingstate). FIG. 21 is an explanatory view showing a state that the portableradio device of this embodiment is held by the right hand at aninclination angle of 60 degrees.

As shown in FIG. 22, when the antenna element 101 side is selected bythe high frequency switch 111, since the lower case 105 is held by thehand similarly to the case of the left hand, the radiation of radio wavefrom the circuit board 103 provided in the lower case 105 is decreasedand the radiation from electric current 115 on the antenna element 101has a control. As a result, the vertically polarized wave (Eθ) componenton the horizontal (XY) plane is higher than that when the antennaelement 102 is selected. Accordingly, as shown in FIG. 23, in thedirectivity on the horizontal plan (XY plane), the directivity 123 ofthe vertically polarized wave (Eθ) component is higher in the directionof a −Y side (right hand side) than the directivity 124 of thehorizontally polarized wave (Eφ) component.

On the other hand, as shown in FIG. 24, when the antenna element 102side is selected by the high frequency switch 111 the radiation from anelectric current 118 due to a vector synthesis of an electric current116 on the antenna element 102 and an electric current 117 on theantenna element 101 electro-magnetically connected to the electriccurrent 116 has a control. As a result, the vertically polarized wave(Eθ) component on the horizontal (XY) plane is higher than that when theantenna element 101 is selected. As a result, the horizontally polarizedwave (Eφ) component on the horizontal (XY) plane is increased.Accordingly, as shown in FIG. 25, in the directivity on the horizontal(XY) plane, the directivity 126 of the horizontally polarized wave (Eφ)component is higher in the direction of the −Y side (right hand side)than the directivity 125 of the vertically polarized wave (Eθ)component.

As shown in FIG. 25, the PAG obtained when the antenna element 1 isselected is −11 dBd (dipole ratio gain). On the other hand, the PAGobtained when the antenna element 102 is selected is −14 dBd, which islower by 3 dB than the former. Accordingly, in the right hand speakingstate, when the antenna element 101 is selected, the PAG becomes higher.

As described above, in the portable radio device of this embodiment,when the upper case 104 and the lower case 105 are opened, either theantenna element 101 or the antenna element 102 having a higher antennaperformance is selected. When the upper case and the lower case areclosed, the antenna element 2 side is forcedly selected. Thus, the highantenna performance can be ensured in any of the opening and closingstates. Further, when in the right hand speaking state, the antennaelement 1 is selected, and, in the left hand speaking state, the antennaelement 102 is selected, the high antenna gain as large as −11.5 dBd canbe obtained in any state of the left hand speaking and the right handspeaking.

In this embodiment, as shown in FIG. 14, the feeding point 108 of theantenna element 101 is arranged at the right (Y) side and the feedingpoint 113 of the antenna element 102 is arranged at the left (−Y) side.When the arrangement of these feeding points is reversed, the tendencyof the PAG in the left hand speaking state and the right hand speakingstate is reversed. Even in this case, effects by the above-describeddiversity operation can be likewise obtained. Further, as an antennaelement opposed to the antenna element 101 and the antenna element 102,the circuit board 103 provided in the lower case 105 is used. However,this antenna element may be, for instance, a metallic plate forshielding the circuit or a conductor plate provided exclusively for theantenna element.

Eighth Embodiment

FIG. 26 is a front view showing a portable radio device for explainingan eighth embodiment of the present invention. As shown in FIG. 26, theportable radio device of the eighth embodiment includes an upper case210 as one example of a first casing and a lower case 211 as one exampleof a second casing connected to the upper case 210 by a hinge portion212 a as one example of a connection portion so as to freely rotate. Theupper case 210 and the lower case 211 are made of molded products of aresin as an insulator.

In the front surface (the direction of an X side) of the upper case 210,a sound port 213 for guiding sound generated in a sound generatingelement such as a speaker provided in the upper case 210 to an externalpart is provided. The sound port 213 is provided so as to be locatednear the ear of a user when the user holds a foldable or collapsibleportable telephone device 201 by a hand to speak.

In the upper case 210, a plate shaped conductor 202 is arranged as oneexample of a first antenna element. In the dimensions of the plateshaped conductor 202, for instance, a long side L21 has 90 mm and ashort side L23 has about 45 mm. In the lower end (−Z side) of the plateshaped conductor 202, a feeding point 203 is provided in a left end (−Yside) and a feeding point 204 is provided in a right end (Y side). Tothe feeding point 203 and the feeding point 204, a matching circuit 205and a matching circuit 206 are respectively connected through feeders(an illustration is omitted) or the like.

In the lower case 211, a circuit board 221 is provided. On the circuitboard 221, circuit elements for realizing the functions of the portableradio device are mounted and the matching circuits 205 and 206, a switch223, a radio circuit 224 and a control circuit 225 are disposed. In thedimensions of the circuit board 221, for instance, a long side L22 has90 mm and a short side L23 has about 45 mm. On the circuit board 221, aground pattern (an illustration is omitted) as the earth potential ofthe circuit is formed in a substantially entire surface.

In the matching circuit 205 and the matching circuit 206, the groundends of the matching circuit 205 and the matching circuit 206 arerespectively grounded in the ground pattern on the circuit board 221.The switch 223 is switched to select either the matching circuit 205 orthe matching circuit 206. The selected matching circuit is connected tothe radio circuit 224. Here, the switch 223 shows one example of aswitching portion and is a high frequency switch composed of, forinstance, an FET or a PIN diode. The radio circuit 224 includes areceiving circuit and a transmitting circuit. Further, the controlcircuit 225 detects a receiving signal level in the radio circuit 224and controls the switch 223 to switch so as to select the matchingcircuit 205 or the matching circuit 206 in which the receiving signallevel is constantly high.

In the above-described structure, the plate shaped conductor 202 and theground pattern formed on the circuit board 221 operate as a dipoleantenna. The matching circuit 205 and the matching circuit 206 match theimpedance of the plate shaped conductor 202 with the circuit impedance(ordinarily, 50Ω) of the radio circuit 224.

Now, an antenna operation of the portable radio device according to theeighth embodiment will be described by way of an example in whichoperating frequency is set to 1.5 GHz.

FIG. 27 is a diagram showing the antenna operation when the switch 223is switched to select the matching circuit 205, that is, the feedingpoint 203. In FIG. 27, parts designated by the same reference numeralsas those of FIG. 26 show the same components.

As shown in FIG. 27, when the feeding point 203 side is selected, afeeding source 230 is connected to the feeding point 203 in the left end(−Y side) of the plate shaped conductor 202 and a feeding point 231 inthe left end (−Y side) of the circuit board 221.

FIG. 28 shows a directivity of a dipole antenna on a YZ plane when theswitch 223 is switched to select the matching circuit 205. As shown bythe directivity 240 a in FIG. 28, an antenna gain in the direction of Yis higher by about 5 dB than a gain in the direction of −Y.

FIG. 29 shows a state that the user holds the portable radio device by aleft hand- to speak. Under this state, the portable radio device is heldso that the sound port 213 (see FIG. 26) directed to the front surface,that is, to the direction of X is located near the left ear of the user.At this time, as shown in FIG. 29, the direction of Y in a coordinatesystem in FIG. 26 is directed to a direction inclined slightly forwardviewed from the direction of a vertex by the user. As shown in FIG. 28,when the switch 223 is switched to select the feeding point 203, theantenna gain in the direction of Y is higher than that in the directionof −Y. Thus, in FIG. 29, the antenna gain is high in the direction ofthe vertex and low in the direction of the shoulder of the user.Accordingly, an influence of the shoulder of the user is reduced and anantenna performance in a speaking state when the user holds the portableradio device by the left hand is increased.

FIG. 30 is a diagram showing an antenna operation when the switch 223 isswitched to select the matching circuit 206, that is, the feeding point204. In FIG. 30, parts designated by the same reference numerals asthose of FIG. 26 show the same components.

As shown in FIG. 30, when the feeding point 204 side is selected, afeeding source 232 is connected to the feeding point 204 at the rightend (Y side) of the plate shaped conductor 202 and a feeding point 233at the right end (Y side) of the circuit board 221.

FIG. 31 shows a directivity of a dipole antenna on the YZ plane when theswitch 223 is switched to select the matching circuit 206. As shown bythe directivity 240 b in FIG. 31, an antenna gain in the direction of −Yis higher by about 5 dB than an antenna gain in the direction of Y. Thatis, the directivity 240 b shows opposite characteristics to those of thedirectivity shown in FIG. 28.

FIG. 32 shows a state that the user holds the portable radio device by aright hand to speak. As described above, when the switch 223 is switchedto select the feeding point 204, since the antenna gain in the directionof −Y is higher than that in the direction of Y, the antenna gain ishigh in the direction of the vertex and low in the direction of theshoulder of the user. Accordingly, an influence of the shoulder of theuser is reduced to improve an antenna performance under a speaking statein which the user holds the portable radio device by the right hand.

In this embodiment, the two feeding points are arranged at the left endand the right end of the plate shaped conductor 202. However, forinstance, three or more feeding points may be disposed at differentpositions and they may be switched. In this case, tree or more ofdifferent directivities can be obtained.

Further, the dimensions of the plate shaped conductor 202 and thecircuit board 221 are not limited to those shown in the eighthembodiment. When the ratio of the length of the short side to the lengthof long side is about ⅕ or higher, an effect of switching thedirectivity may be obtained.

Further, the control circuit 225 detects the direction of the portableradio device, that is, by which of the hands the user holds the portableradio device. The switch 223 may be switched in accordance with thedetected results. In that case, the control circuit 225 is notnecessarily connected to the radio circuit 224.

In the portable radio device according to the eighth embodiment of thepresent invention, a plurality of feeding portions are provided in theplate shaped conductor and these feeding-portions are switched by theswitch 223, so that the directivity of an antenna can be changed.Further, a directional diversity effect can be obtained without addingantenna elements for diversity. Further, even when the portable radiodevice is held either the left hand or the right hand under the speakingstate, a high antenna performance can be obtained.

Ninth Embodiment

FIG. 33 is a front view showing a portable radio device for explaining aninth embodiment of the present invention. FIG. 34 is a side viewshowing the portable radio device for explaining the ninth embodiment ofthe present invention. In FIGS. 33 and 34, duplicated portions to thoseof FIG. 26 are designated by the same reference numerals and theexplanation thereof is omitted.

As shown in FIGS. 33 and 34, the portable radio device of the ninthembodiment employs a structure that an upper case 210 is connected to alower case 211 by a hinge portion 212 b and may have two statesincluding an opening state and a closing state by rotating the cases onthe hinge portion 212 b.

In the front surface side (a side in the direction of X) of the uppercase 210 in the drawing, that is, on a surface having a sound port 213arranged, a metallic frame 214 is mounted. For the metallic frame 214,light metal having high electric conductivity and high strength, forinstance, magnesium alloy is used. Such kind of metal is used so thatthe strength of the thin upper case 210 can be ensured and the metallicframe 214 can function as an antenna element. The length L26 of the longside of the metallic frame 214 has, for instance, about 90 mm. The outerpackage surface of the metallic frame 214 is ordinarily painted fordressing. Here, an explanation thereof is omitted.

In the lower case 211, a circuit board 221 is provided. In the circuitboard 221, matching circuits 222 a and 222 b, a switch 223, a radiocircuit 224 and a control circuit 225 are arranged.

The hinge portion 212 b includes hinge fittings 215 a and 215 b forconnecting the upper case 210 to the lower case 211, hinge fittings 219a and 219 b provided in the lower case 211, and rotating shafts 218 aand 218 b for connecting the hinge fittings 215 a and 215 b to the hingefittings 219 a and 219 b so as to respectively freely rotate.

In both the right and left side parts (directions of ±Y) of the lowerend (−Z side) of the metallic frame 214, tapped holes for attaching themetallic frame 214 to the upper case 210 are opened. On the hingefittings 215 a and 215 b formed in L shapes, tapped holes for attachingthem to the upper case 210 are opened. Attaching screws 216 are attachedto tapped hole parts 217 of the upper case 210 respectively through thetapped holes of the metallic frame 214 and the hinge fittings 215 a and215 b. According to this structure, the metallic frame 214 iselectrically connected to the hinge fittings 215 a and 215 b, and theupper case 210 and the metallic frame 214 are mechanically fixed to thehinge fittings 215 a and 215 b.

The hinge fitting 215 a is connected to the hinge fitting 219 a providedin the left side (−Y side) of the upper end (Z side) of the lower case211 through the rotating shaft 218 a so as to freely rotate. The hingefitting 215 b is connected to the hinge fitting 219 b provided in theright side (Y side) of the upper end (Z side) of the lower case 211through the rotating shaft 218 b so as to freely rotate.

In the hinge fittings 219 a and 219 b, tapped holes for attaching themto the lower case 211 are opened. Further, in feeding terminals 220 aand 220 b, tapped holes are also opened. Attaching screws 229 areattached to tapped hole parts 226 (FIG. 34) of the lower case 211through the tapped holes of the feeding terminals 220 a and 220 b andthe hinge fittings 219 a and 219 b. According to this structure, thehinge fittings 219 a and 219 b are respectively electrically connectedto the feeding terminals 220 a and 220 b, and the lower case 211, thehinge fittings 219 a and 219 b and the feeding terminals 220 a and 220 bare respectively mechanically fixed.

The hinge fittings 215 a and 215 b, the rotating shafts 218 a and 218 band the hinge fittings 219 a and 219 b are respectively made ofelectrically conductive metal and are electrically conducted at contactpoints between them. Accordingly, the metallic frame 214 is electricallyconnected to the feeding terminals 220 a and 220 b through the attachingscrews 216, the hinge fittings 215 a and 215 b, the rotating shafts 218a and 218 b, the hinge fittings 219 a and 219 b and the attaching screws229 and mechanically fixed.

In the lower case 211, the matching circuit 222 a is arranged in theleft end (a side in the direction of −Y) part of the upper end (the sideof the direction of Z). The matching circuit 222 a is connected to thefeeding terminal 220 a. Further, the matching circuit 222 b is arrangedin the right end (a side in the direction of Y) part of the upper end(the side in the direction of Z) of the lower case 211. The matchingcircuit 222 b is connected to the feeding terminal 220 b. The feedingterminal 220 a is connected to the matching circuit 222 a by, forinstance, a spring contact or solder. Similarly, the feeding terminal220 b is connected to the matching circuit 222 b on the circuit board221 provided in the lower case 211, by for instance, a spring contact orsolder. The long side L24 of the circuit board 22 has, for instance,about 90 mm.

The matching circuit 222 a is connected to a terminal a of the switch223 on the circuit board 221. The matching circuit 222 b is connected toa terminal b of the switch 223. The ground ends (an illustration isomitted) of the matching circuits 222 a and 222 b are grounded in aground pattern on the circuit board 221. The switch 223 is switched toselect either the matching circuit 222 a or 222 b and the selectedmatching circuit is connected to the radio circuit 224. Here, the switch223 is a high frequency switch formed with, for instance, an FET or aPIN diode. The radio circuit 224 includes a receiving circuit and atransmitting circuit or the like. The control circuit 225 detects areceiving signal level in the radio circuit 224 and controls the switch223 to switch so as to select the matching circuit 222 a or the matchingcircuit 222 b in which the receiving signal level is constantly high.

According to the above-described structure, the metallic frame 214 andthe hinge portion 212 b and the ground pattern on the circuit board 221operate as a dipole antenna. At this time, the metallic frame 214 andthe hinge portion 212 b operate as a first antenna element having thelength of L25 (for instance, 110 mm). The matching circuits 222 a and222 b match the impedance of the first antenna element with the inputimpedance (ordinarily, 50Ω) of the radio circuit 224. Further, theground pattern on the circuit board 221 having the length of L24operates as a second antenna element. Here, a gap G between the hingefittings 219 a and 219 b and the ground pattern on the circuit board 221is desirably wide as much as possible (for instance, 2 mm or more, orwhen the portable radio device is used with 800 MHz, λ/20 or more) fromthe viewpoint of an antenna performance.

Now, an antenna operation of the portable radio device having theabove-described structure will be described below.

When the switch 223 is switched to select the matching circuit 222 aside, that is, the feeding terminal 220 a side, characteristics near thedirectivity 240 a shown in FIG. 28 are obtained. When the switch 223 isswitched to select the matching circuit 222 b side, that is, the feedingterminal 220 b side, characteristics near the directivity 240 b shown inFIG. 31 are obtained. Accordingly, a directional diversity effect can beobtained for arriving radio waves inputted to the portable radio devicefrom various directions.

Further, as shown in FIG. 29, in the speaking state in which theportable radio device is held by the left hand, the matching circuit 222a is selected to obtain a high antenna performance. On the contrary, asshown in FIG. 32, in the speaking state in which the portable radiodevice is held by the right hand, the matching circuit 222 b isselected. Under this state, the high antenna performance can be likewiseobtained. Accordingly, the switch 223 is switched to select either ofthe matching circuit 222 a and the matching circuit 222 b so that astate can be selected in which the antenna performance is increasedcorrespondingly to both the states that the portable radio device isheld by the left hand or the right hand under the speaking state.

In the ninth embodiment, the two feeding portions are arranged at theleft end and the right end of the plate shaped metallic frame 214.However, for instance, three or more feeding portions may be disposed atdifferent positions and they may be switched. In this case, tree or moreof different directivities can be obtained.

Further, the dimensions of the metallic frame 214 and the circuit board221 are not limited to those shown in the ninth embodiment. When theratio of the short side to the long side is about ⅕ or higher, an effectof switching the directivity may be obtained.

Further, in the ninth embodiment, the two hinge fittings are spacedapart right and left and attached to the right and left sides. However,even when the hinge fitting 219 a is formed integrally with the hingefitting 219 b, if a plurality of feeding portions is provided atprescribed intervals, the same effects can be obtained.

Further, the control circuit 225 detects the direction of the portableradio device, that is, by which of the hands the user holds the portableradio device. The switch 223 may be switched in accordance with thedetected results. In that case, the control circuit 225 is notnecessarily connected to the radio circuit 224.

In the ninth embodiment, the hinge fittings 215 a and 215 b, therotating shafts 218 a and 218 b and the hinge fittings 219 a and 219 bare respectively electrically conducted together. However, they may beelectro-magnetically connected together by a capacitive reactance.

In the portable radio device according to the ninth embodiment of thepresent invention, a plurality of feeding portions are connected to thehinge portions connected to the metallic frame and these feedingportions are switched by the switch, so that the directivity of anantenna can be changed. Further, a directional diversity effect can beobtained without adding antenna elements for diversity. Further, evenwhen the portable radio device is held either the left hand or the righthand under the speaking state, a high antenna performance can beobtained. Further, the metallic frame forming a part of the upper casehas a function of the antenna element. Thus, the decrease of thicknessof the portable radio device can be realized.

Tenth Embodiment

FIG. 35 is a front view showing a portable radio device for explaining atenth embodiment of the present invention. In FIG. 35, duplicatedportions to those of FIG. 26 are designated by the same referencenumerals and the explanation thereof is omitted.

As shown in FIG. 35, in the portable radio device according to the tenthembodiment, a hinge portion 212 c that includes a hinge fitting 215 cprovided between hinge fittings 215 a and 215 b, a rotating shaft 218 cattached to the hinge fitting 215 c so as to freely rotate and a hingefitting 219 c attached to the rotating shaft 218 c so as to freelyrotate is attached to an upper case 210. To the hinge portion 212 c, afeeding terminal 220 c attached to the hinge fitting 219 c is connected.The feeding terminal 220 c is connected to a matching circuit 228disposed on a circuit board 221 by a spring contact or solder or thelike. The matching circuit 228 is connected to a radio circuit 224.Further, the ground end (an illustration is omitted) of the matchingcircuit 228 is grounded in a ground pattern (an illustration is omitted)of the circuit board. In the tenth embodiment, the feeding terminal 220c and the matching circuit 223 show one examples of a feeding portion.

A switch 227 a is connected between a feeding terminal 220 a and theground pattern (the illustration is omitted) of the circuit board 221. Aswitch 227 b is connected between a feeding terminal 220 b and theground pattern (the illustration is omitted) of the circuit board 221.In the tenth embodiment the feeding terminals 220 a and 220 b show oneexamples of a ground portion.

The switches 227 a and 227 b are high frequency switches formed by, forinstance, an FET or a PIN diode like the switch 223 shown in FIG. 33. Acontrol circuit 225 detects a receiving signal level in the radiocircuit 224 and controls the switch (switches 227 a and 227 b) in whichthe receiving signal level is always high to be selected.

An antenna operation of the portable radio device constructed asdescribed above will be described below.

In FIG. 35, when the switch 227 a is turned ON and the switch 227 b isturned OFF, the directivity of an antenna is high in a gain in thedirection of Y like the directivity 260 a shown in FIG. 36. On thecontrary, when the switch 227 a is turned OFF and the switch 227 b isturned ON, the directivity of an antenna is high in a gain in thedirection of −Y like the directivity 260 b shown in FIG. 37. Further,when both the switch 227 a and the switch 227 b are turned OFF, anintermediate directivity of the directivity 260 a and the directivity260 b is obtained. When both the switch 227 a and the switch 227 b areturned ON, antenna characteristics are deteriorated. Therefore, thecontrol operation of the control circuit 225 is desirably set not toselect this state.

Accordingly, a directional diversity effect that can control three kindsof directivities for arriving radio waves inputted to the portable radiodevice from various directions can be obtained.

Further, in the speaking state shown in FIG. 29 obtained when theportable radio device is held by the left hand, the switch 227 a isturned ON and the switch 227 b is set to OFF. Thus, a high antennaperformance is obtained. On the contrary, in the speaking state as shownin FIG. 32 obtained when the portable radio device is held by the righthand, the switch 227 a is turned OFF and the switch 227 b is set to ON.Under this state, the high antenna performance is also obtained.

In the tenth embodiment, the feeding portion is disposed at a centralportion and the two ground portions for switching a ground are disposedat both ends. However, even when the feeding portion is disposed at oneend and the ground portion is disposed at one end opposed thereto, adirectional diversity effect can be obtained.

Further, the control circuit 225 detects the direction of the portableradio device, that is, by which of the hands the user holds the portableradio device. The switch 223 may be switched in accordance with thedetected results. In that case, the control circuit 225 is notnecessarily connected to the radio circuit 224.

In the tenth embodiment, the hinge fittings 215 a, 215 b and 215 c, therotating shafts 218 a, 218 b and 218 c and the hinge fittings 219 a, 219b and 219 c are respectively electrically conducted together. However,they may be electro-magnetically connected together by a capacitivereactance.

In the portable radio device according to the tenth embodiment of thepresent invention, the feeding portion and a plurality of groundportions are connected to the hinge portions connected to a metallicframe and the ground portions are switched by the switch, so that thedirectivity of an antenna can be changed. Further, a directionaldiversity effect can be obtained without adding antenna elements fordiversity. Further, even when the portable radio device is held eitherthe left hand or the right hand under the speaking state, a high antennaperformance can be obtained. Further, the metallic frame forming a partof the upper case has a function of the antenna element. Thus, thedecrease of thickness of the portable radio device can be realized.

The present invention is described in detail by referring to thespecific embodiments, however, it is to be understood to a person withordinary skill in the art that various changes or modifications may bemade without departing the spirit and the scope of the presentinvention.

This application is based on Japanese Patent Application (No.2002-210612) filed in Jul. 19, 2002, Japanese Patent Application (No.2003-015675) filed in Jan. 24, 2003, and Japanese Patent Application(No. 2003-167962) filed in Jun. 12, 2003 and the contents thereof aretaken in as references.

INDUSTRIAL APPLICABILITY

As described above, the portable radio device according to the presentinvention can obtain a high performance in various using states.

1. A portable radio device comprising: a first casing; a second casing;at least two connection portions, each connection portion connecting thefirst casing to the second casing so as to freely rotate through arotation shaft provided in each of the at least two connection portions;a first antenna element, provided in the first casing; a conductorelement, provided in the second casing; and at least two feedingportions provided in the second casing, each feeding portion having oneend electrically connected to the first antenna element through each ofthe at least two connection portions including the rotation shaft andthe other end electrically connected to the conductor element, whereinthe connection portion including the rotation shaft has electricconductivity to form a dipole antenna as a whole by the first antennaelement, the connection portion and the conductor element, wherein theconnection portion is arranged away from the conductor element at adistance, and wherein the feeding portions are separate from each otheralong the rotation shaft in a prescribed gap, wherein the electricalconnection between the first antenna element and the conductor elementis switchable among at least two routes, each route electricallyconnecting the first antenna element to the conductor element througheach different one of the feeding ports and each different one of theconnection portions, to change a directivity of the dipole antenna. 2.The portable radio device as set forth in claim 1, wherein a pluralityof first antenna elements are provided in the first casing; and theportable radio device further comprising a switching portion whichswitches the plurality of first antenna elements so as to connect to thefeeding portion.
 3. The portable radio device as set forth in claim 2,wherein the switching portion switches whether the plurality of thefirst antenna elements are electrically connected to the feeding portionor the plurality of the first antenna elements are electricallyconnected to the conductor element, respectively.
 4. The portable radiodevice as set forth in claim 2, further comprising a half-wavelengthelement being electrically connected between at least one of theplurality of the first antenna elements and the switching portion. 5.The portable radio device as set forth in claim 2, further comprising aplurality of half-wavelength elements being respectively electricallyconnected to the plurality of the first antenna elements, wherein theswitching portion selectively switches the plurality of the firstantenna elements and the plurality of the half-wavelength elements so asto connect to the feeding portion.
 6. The portable radio device as setforth in claim 2, further comprising: a casing opening and closing statedetecting portion, detecting whether or not the first casing and thesecond casing are opened to each other; and a control portion,controlling the switching portion in accordance with the detected resultof the casing opening and closing state detecting portion.
 7. Theportable radio device as set forth in claim 2, further comprising acontrol portion, determining a receiving level of a radio circuitportion to control the switching portion so as to raise the receivinglevel.
 8. The portable radio device as set forth in claim 1, furthercomprising a plurality of impedance matching portions respectivelycorresponding to the plurality of the first antenna elements.
 9. Theportable radio device as set forth in claim 1, wherein the antennaelement and the conductor element are respectively formed in plateshapes along the surface of the first casing and the second casing. 10.The portable radio device as set forth in claim 9, further comprising: acircuit board, provided in the second casing and having a radio circuit,wherein the conductor element is formed in a ground pattern which isformed on the circuit board provided in the second casing; wherein aground of the radio circuit portion is electrically connected to theground pattern; and wherein the feeding portion is provided in the radiocircuit portion.
 11. A portable radio device as set forth in claim 1,further comprising: a second antenna element, provided in the secondcasing near the connection portion; an opening and closing statedetecting portion, detecting the opening and closing states of the firstcasing and the second casing; and a switching portion, selecting andswitching any one of the first antenna element and the second antennaelement to a connection to a signal processing portion for performing asignal process in accordance with the detected result of the casingopening and closing state detecting portion, wherein when the firstcasing and the second casing are opened, the first antenna element andthe conductor element form the dipole antenna; and wherein when thefirst casing and the second casing are closed, the second antennaelement and the conductor element form a mono-pole antenna.
 12. Theportable radio device as set forth in claim 11, wherein when the firstcasing and the second casing are opened, the switching portion selectsthe first antenna element; and wherein when the first casing and thesecond casing are closed, the switching portion selects the secondantenna element.
 13. The portable radio device as set forth in claim 11,further comprising: a first matching portion, matching the impedance ofthe first antenna element to a prescribed value; and a second matchingportion, matching the impedance of the second antenna element to aprescribed value.
 14. The portable radio device as set forth in claim 1,further comprising: a second antenna element provided in the secondcasing near the connection portion; a receiving field intensitymeasuring portion, measuring the receiving field intensity of a signalreceived by the first antenna element or the second antenna element; anda switching portion, selecting and switching the antenna element havinga higher receiving field intensity to a connection to a signalprocessing portion for performing a signal process in accordance withthe measured result of the receiving field intensity measuring portion,wherein the first antenna element has a first feeding point forelectrically connecting to the conductor element; wherein the secondantenna element has second feeding point for electrically connecting tothe conductor element; and wherein the first feeding point and thesecond feeding point are provided at the diagonal positions of opposedsides when the first casing and the second casing are opened.
 15. Theportable radio device as set forth in claim 1, further comprising: acircuit board, provided in the second casing; a plurality of feedingportions, feeding electric current to the antenna element and beingseparated to each other; a radio circuit, disposed in the circuit board;and a switching portion, provided between the plurality of feedingportions and the radio circuit and selecting any one of the plurality ofthe feeding portions to connect the radio circuit.
 16. The portableradio device as set forth in claim 15, further comprising: a controlcircuit, controlling the switching portion in accordance with the levelof a receiving signal received by the radio circuit.
 17. The portableradio device as set forth in claim 1, further comprising: a circuitboard, provided in the second casing; a radio circuit, disposed in thecircuit board and electrically connected to the feeding portion; aground portion, spaced from the feeding portion and connecting theantenna element to the circuit board; and a switching portion, switchingwhether the ground portion is connected to the circuit board or theground portion and the circuit board are opened.
 18. The portable radiodevice as set forth in claim 17, wherein a plurality of ground portionsare provided; and wherein the ground portions are disposed so as to bespaced apart in the end part of the antenna element connected to thesecond casing.
 19. The portable radio device as set forth in claim 18,wherein the switching portion switches the ground portions respectively.20. The portable radio device as set forth in claim 17, wherein theconnection portion has an electric conductivity; and wherein the groundportion is electrically connected to the antenna element through theconnection portion.
 21. The portable radio device as set forth in claim1, wherein the first antenna element is an electric conductive frameforming a part of the first casing.
 22. The portable radio deviceaccording to claim 21, wherein the conductor element is a ground patternprovided on a circuit board.
 23. The portable radio device according toclaim 1, wherein each of the at least two connection portions includes afirst hinge portion provided in the first casing and a second hingeportion provided in the second casing, wherein the first hinge portionis connected to an end of the first antenna element, and wherein thesecond hinge portion is arranged away from the conductor element at thedistance, and connected to each of the at least two feeding portions.24. The portable radio device according to claim 23, wherein theconnection portion is configured so that a capacity reactance occursbetween the first hinge portion and the second hinge portion.
 25. Theportable radio device according to claim 1, wherein each of the at leasttwo connection portions is connected to each of the at least two feedingportions, respectively.
 26. The portable radio device according to claim1, further comprising a switching portion provided in the second casing,and adapted to select any one of the at least two feeding portions to beelectrically connected to a radio circuit disposed in the second casing.27. A portable radio device comprising: a first casing; a second casing;at least two connection portions, each connection portion connecting thefirst casing to the second casing so as to freely rotate through arotation shaft provided in each of the at least two connection portions;a first antenna element, provided in the first casing; a conductorelement, provided in the second casing; and at least two feedingportions provided in the second casing, each feeding portion having oneend electrically connected to the first antenna element through each ofthe at least two connection portions including the rotation shaft andthe other end electrically connected to the conductor element, whereinthe connection portion including the rotation shaft has electricconductivity to form a dipole antenna as a whole by the first antennaelement, the connection portion and the conductor element, wherein theconnection portion is arranged away from the conductor element at adistance, and wherein the feeding portions are separate from each otheralong the rotation shaft in a prescribed gap, wherein each of the atleast two connection portions includes a first hinge portion provided inthe first casing and a second hinge portion provided in the secondcasing, wherein the first casing and the first antenna element aremechanically fixed to each of the first hinge portions, and wherein thesecond casing, each of the second hinge portions and each of the atleast two feeding portions are respectively mechanically fixed.